The present invention refers to a process for the removal of residues, in particular of unfixed dyes, dye degradation products, chemical and/or processing agent residues from textile substrates.
When textiles are finished these textile substrates are frequently brought into contact with substances intended to bring about some change in the textile substrates and processed accordingly. Thus, for example, the textile substrates are cleaned, bleached, softened, dyed and/or printed, whereby during each of the finishing processes described, residues are produced, which have to be removed from the textile substrate treated, in order to avoid the occurrence of interference in the processes carried out later.
In order to ensure such removal of residues, in particular unfixed dyes, dye degradation products, chemical and/or processing agent residues, from the textile substrates that have been treated it is a known procedure to place these textile substrates in an apparatus and there to expose them to the influence of an aqueous liquor. In a discontinuous process of this type, depending on the batch size, between ca. 2 kg and 1 000 kg textile substrate is placed in the appropriate apparatus and there treated at a liquor ratio (mass textile substrate:mass liquor) of between 1:3 and 1:50. On account of the fact that certain residues can only be removed from the textile substrate with difficulty, a large number of rinsing baths are required in the processes known today, because as soon as a particular rinsing bath is accordingly loaded with residues, the complete rinsing bath is removed and the textile substrate is treated once again with a fresh rinsing bath. Since it is generally necessary, depending on the type of residue, to repeat such a rinsing process between two and eight times, such discontinuous rinsing requires considerable quantities of water, that is, for example, between 20 litres and 800 litres per kg textile substrate.
In overflow rinsing, which is also practised, the outlet valve remains open during the addition of fresh water so that with the passage of time a constant amount of water is introduced and at the same time a constant amount of water is removed. However, such overflow rinsing does not, in general, lead to a reduction worth mentioning in the aforementioned amounts of water required for batch-wise rinsing.
The known aforementioned processes possess the disadvantage that they are uneconomic and ecologically dubious on account of the large quantities of water required.